The present invention relates to a process for the production of 1,1,2-trichloro-2-methylpropane by the reaction of 1-chloro-2-methylpropene with sulfuryl chloride, preferably in the presence of light, especially UV light and/or in the presence of an aldehyde as the catalyst.
No process has been known heretofore permitting the production of 1,1,2-trichloro-2-methylpropane selectively from C.sub.4 -compounds. This compound can be used for several purposes, e.g. as a starting material for the preparation of pharmaceuticals and of insecticides as well as an intermediate for other C.sub.4 -derivatives, this compound is expected to become more interesting for organic reactions, since it is now readily available for the first time.
In the prior art, this compound has been obtained as a by-product from various reactions. For example, this compound is obtained in minor quantities in the direct chlorination of isobutene, as a higher-chlorinated by-product which is difficult to isolate. The primary products are 3-chloro-2-methylpropene and 1-chloro-2-methylpropene. Also produced are other tri-, tetra-, and pentachloro derivatives.
Photochemical chlorination of isobutene in the gaseous phase also yields 1,1,2-trichloro-2-methylpropane merely as a by-product [Beilstein E III 1, p. 320 (1958) : Ing. eng. Chem. 40 (1948) : 1488].
Further chlorination of already partially chlorinated C.sub.4 -compounds likewise takes place with little selectivity. Thus, the chlorination of 2-chloro- and 1,2-dichloro-2-methylpropane in the liquid phase yields 1,1,2-trichloro-2-methylpropane only as a by-product [Beilstein E III 1, p. 320 (1958) : Am. Soc. 58 (1936) : 1028, 1029], even if the process is conducted in the presence of AlCl.sub.3 [Beilstein E IV 1, p. 293 (1972) : Bl. Chem. Soc. Japan 30 (1957) : 218, 220].
Chlorination of 1-chloro-2-methylpropene in the presence of sodium bicarbonate at 0.degree. C. yields, besides 68% 3,3-dichloro-2-methylpropene, only 32%, 1,1,2-trichloro-2-methylpropane [Chem. Abstr. 33 (1939) : 4190].
All of these conventional processes have the common disadvantage that the desired 1,1,2-trichloro-3-methylpropane is obtained only as a by-product.